The existing user equipments (UE) basically can support short-range communication technology and cellular communication technology simultaneously. The cellular communication technology can be, such as a long term evolution (LTE), a universal mobile telecommunications system (UMTS), code division multiple access (CDMA), a global system for mobile communications (GSM), a general packet radio service (GPRS) and worldwide interoperability for microwave access (WiMAX). The short-range wireless communication generally refers to a technology of providing wireless communications within a smaller area (such as, hundreds of meters), and the existing common short-range wireless communication technologies include: institute of electrical and electronics engineers (IEEE) 802.11 wireless local area network (WLAN), IEEE802.15 wireless personal area network (WPAN), home radio frequency (HomeRF), infrared transmission technology, and LTE-device to device (LTE-D2D), etc.
LTE aims to provide a low-cost network capable of reducing the time delay, raising the user data rate, and improving the system capacity and coverage. The LTE adopts packet switch (PS) domain services, and the bearer networks are all Internet protocol (IP) bearers.
Hereinafter, the illustration is made by taking LTE in cellular communication technologies and wireless fidelity (WiFi) in short-range communication technologies as an example, and various combinations of other short-range communication technologies and cellular communication technologies are similar to this, and no further details are given here. The WiFi is a type of short-range communication technology based on IEEE 802.11.
A determined user-plane bearer in a LTE network is as shown in FIG. 1, and the air interface protocol stack between a UE and an evolved node B (eNB) from top to bottom includes: a packet data convergence protocol (PDCP), a radio link control (RLC), a media access control (MAC) and a physical layer (PHY). A GPRS tunneling protocol for user plane (GTP-U) is a tunnelling protocol within the network. The functions of the MAC layer between the physical layer and the RLC layer mainly include: hybrid automatic repeat-request (HARQ), logical channel to transport channel mapping, multiplexing, demultiplexing and random access control, etc. The MAC layer of the base station also has a function of scheduling UE.
The base station can schedule all the UEs in an active state under the base station, that is, the base station selects one or more UEs to send or receive data in certain time domain and frequency domain resources. The base station selects the UE by ranking all the UEs in the active state under the base station according to the scheduling ranking algorithm, and then selects the highest ranked UE to perform priority scheduling. For example, if the base station performs scheduling with a granularity of one or more resource blocks, then the base station ranks all the UEs in the active state under the base station according to the scheduling ranking algorithm in each granularity, and then selects the highest ranked UE to perform priority scheduling.
The commonly-used scheduling ranking algorithm can be a proportional fair (PF) algorithm, and the basic idea is to rank the result of dividing a channel quality indicator (CQI) of each UE by an average rate (AR), namely CQI/AR, in each granularity, and then selects the highest ranked UE to perform priority scheduling. Where the “/” represents division. If taking five resource blocks as a granularity, rank every five resource blocks, select a UE with the highest CQI/AR, and schedule the UE with the highest CQI/AR on the resource of the five resource blocks. It should be noted that, the average rate is obtained through a certain algorithm, such as accumulating several most recently used rates for transmitting data by a certain proportion, and any algorithm for calculating the average rate can be used to perform scheduling ranking on the UE.
In particular, the eNB scheduling UE includes: the eNB notifies, on a physical downlink control channel (PDCCH) and through a scheduling command scrambled by a cell radio network temporary identifier (C-RNTI) of the UE, the UE of using which modulation and coding scheme (MCS) on which (corresponding resource block of) time domain and frequency domain resource to receive data on a physical downlink shared channel (PDSCH). If the eNB schedules a UE, then the UE can detect the scheduling command scrambled by the C-RNTI of itself on the PDCCH, and obtain scheduling control information by decoding PDCCH, and find the data sent to it on the PDSCH according to the time domain and frequency domain resource and the MCS included in the scheduling control information. The data is sent by a MAC packet data unit (MAC PDU). For the UE selected for scheduling, the eNB selects and sends data according to the quality of service (QoS) of its different radio bears (RB), in particular, the eNB can select the data of different radio bears within the UE through scheduling manners such as a token bucket etc. Different radio bearers correspond to different radio bearer-identifiers (RB-ID), and the RB-ID is mapped to a unique logical channel identifier (LCID) on the MAC layer. The MAC layer can learn the radio bearer corresponding to the MAC SDU through the LCID corresponding to each MAC service data unit (MAC SDU) and MAC control element (MAC CE) in the MAC PDU, or learn that the MAC CE with what function corresponds to the LCID. In particular, the radio bearer includes data radio bearer (DRB) and signalling radio bearer (SRB). The LCID corresponding to the SRB is also a fixed value. Generally, the LCID corresponding to the DRB is a value from 3 to 10.
In a traditional method, a first UE selected by scheduling ranking and a second UE actually scheduled by the base station are the same UEs. In particular, the first UE selected by scheduling ranking is the user of data (receiver of downlink data), and the first UE is also referred to as a pre-scheduled UE herein. The second UE actually scheduled by the base station is the UE which is notified by the base station through a scheduling command scrambled by the C-RNTI of the second UE on the PDCCH, of using which MCS on which time domain and frequency domain resource to receive data on the PDSCH, and the second UE is also referred to as an actually-scheduled UE herein.
The basic principle of the current method of multiple UEs cooperative communication (MUCC) is to establish cooperative communication relationship among UEs according to the feature that two or more UEs all support WiFi and LTE at the same time. For example, one UE needs to send or receive data, and one or more other UEs can support the UE and assist the communication, so that reliability and throughput rate can be increased. However, no effective method for performing cooperative communication on the MAC layer is proposed in the current multiple UEs cooperative communication, to make operation of the multiple UEs cooperative communication safe and reliable.